2016-12-10T01:02:33ZDrift-compensated low-noise frequency synthesis based on a CryoCSO for the KRISS-F1(Cs)http://hdl.handle.net/2440/102952
Title: Drift-compensated low-noise frequency synthesis based on a CryoCSO for the KRISS-F1(Cs)
Author: Heo, M.S.; Park, S.E.; Lee, S.B.; Hong, H.G.; Kwon, T.Y.; Park, C.Y.; Lee, W.K.; Yu, D.H.; Hartnett, J.G.
Abstract: This paper reports implementation and operation of a frequency synthesizer based on a cryocooled cryogenic Sapphire oscillator (cryoCSO) for the Cesium atomic fountain clock developing at KRISS, KRISS-Fl(Cs). With use of this highly stable local oscillator, the short-term stability of KRISS-F1(Cs) was greatly improved and reaches the quantum projection noise limit, resulting in the measured lowest Allan deviation of 2.6×10-14. In addition, the long-term drift (4.8×10-14/day) of the cryoCSO could be compensated and reach below 5×10-16/day as low as state-of-the-art active hydrogen masers.2016-01-01T00:00:00ZDrift-compensated low-noise frequency synthesis based on a cryoCSO for the KRISS-F1http://hdl.handle.net/2440/102920
Title: Drift-compensated low-noise frequency synthesis based on a cryoCSO for the KRISS-F1
Author: Heo, M.S.; Park, S.E.; Lee, W.K.; Lee, S.B.; Hong, H.G.; Kwon, T.Y.; Park, C.Y.; Yu, D.H.; Santarelli, G.; Hilton, A.P.; Luiten, A.N.; Hartnett, J.G.
Abstract: In this paper, we report on the implementation and stability analysis of a drift-compensated frequency synthesizer from a cryogenic sapphire oscillator (CSO) designed for a Cs/Rb atomic fountain clock. The synthesizer has two microwave outputs of 7 and 9 GHz for Rb and Cs atom interrogation, respectively. The short-term stability of these microwave signals, measured using an optical frequency comb locked to an ultrastable laser, is better than 5×10−15 at an averaging time of 1 s. We demonstrate that the short-term stability of the synthesizer is lower than the quantum projection noise limit of the Cs fountain clock, KRISS-F1(Cs) by measuring the short-term stability of the fountain with varying trapped atom number. The stability of the atomic fountain at 1 s averaging time reaches 2.5×10−14 at the highest atom number in the experiment when the synthesizer is used as an interrogation oscillator of the fountain. In order to compensate the frequency drift of the CSO, the output frequency of a waveform generator, in the synthesis chain, is ramped linearly. By doing this, the frequency stability of the synthesizer at an average time of one hour reaches a level of 10−16, which is measured with the fountain clock.
Description: Accepted September 9, 2016.2016-01-01T00:00:00ZRecent advances in 3.5 μm erbium doped mid-infrared fiber lasershttp://hdl.handle.net/2440/102919
Title: Recent advances in 3.5 μm erbium doped mid-infrared fiber lasers
Author: Henderson-Sapir, O.; Malouf, A.; Bawden, N.; Munch, J.; Jackson, S.; Ottaway, D.J.
Abstract: The performance of mid-infrared Er3+-doped fiber lasers has dramatically improved in the last few years. In this paper we present an overview of the progress in 3.5 m fiber lasers based on the dual-wavelength pumping approach. The cross-section of the excited state absorption transition used by the 1973 nm second pump is found experimentally. A numerical simulation of the expected Q-switched behavior of this fiber laser is presented. This shows that increasing the power of the 977 nm pump is important to achieve high peak power pulses.2016-01-01T00:00:00ZProteomic responses to gold(III)-toxicity in the bacterium Cupriavidus metallidurans CH34http://hdl.handle.net/2440/102854
Title: Proteomic responses to gold(III)-toxicity in the bacterium Cupriavidus metallidurans CH34
Author: Zammit, C.M.; Weiland, F.; Brugger, J.; Wade, B.; Winderbaum, L.J.; Nies, D.H.; Southam, G.; Hoffmann, P.; Reith, F.
Abstract: The metal-resistant β-proteobacterium Cupriavidus metallidurans drives gold (Au) biomineralisation and the (trans)formation of Au nuggets largely via unknown biochemical processes, ultimately leading to the reductive precipitation of mobile, toxic Au(i/iii)-complexes. In this study proteomic responses of C. metallidurans CH34 to mobile, toxic Au(iii)-chloride are investigated. Cells were grown in the presence of 10 and 50 μM Au(iii)-chloride, 50 μM Cu(ii)-chloride and without additional metals. Differentially expressed proteins were detected by difference gel electrophoresis and identified by liquid chromatography coupled mass spectrometry. Proteins that were more abundant in the presence of Au(iii)-chloride are involved in a range of important cellular functions, e.g., metabolic activities, transcriptional regulation, efflux and metal transport. To identify Au-binding proteins, protein extracts were separated by native 2D gel electrophoresis and Au in protein spots was detected by laser absorption inductively coupled plasma mass spectrometry. A chaperon protein commonly understood to bind copper (Cu), CupC, was identified and shown to bind Au. This indicates that it forms part of a multi-metal detoxification system and suggests that similar/shared detoxification pathways for Au and Cu exist. Overall, this means that C. metallidurans CH34 is able to mollify the toxic effects of cytoplasmic Au(iii) by sequestering this Au-species. This effect may in the future be used to develop CupC-based biosensing capabilities for the in-field detection of Au in exploration samples.
Description: Accepted 11th October 20162016-01-01T00:00:00Z